After almost 200 years at an Eero Saarinen-designed location in the posh Mayfair neighborhood of London, American diplomats will be moving across the Thames to a new headquarters in 2017. And today, Philadelphia-based firm KieranTimberlake took home a hefty commission as its design was selected for the new U.S. Embassy. If you think it looks like a castle, you’re right: The $1 billion EFTE-covered cube even has a moat, which the architects hope will deter any unexpected guests. But the airy fin-like skin and a footprint that appears to almost hover–not to mention the garden notched out of an upper corner–make it feel friendly, transparent and green.

The Los Angeles Times‘ Christopher Hawthorne approves, noting that it “aspires to a different
and broader set of values, primarily having to do with ecological
responsibility and neighborliness within a tight urban fabric.” KieranTimberlake’s win is even more amazing when you see the short-list: They were up against Thom Mayne’s Morphosis, Richard Meier & Partners Architects and Pei Cobb Freed & Partners–all of them Pritzker Prize-winning architects. Here are the renderings from the runners-up.